The present invention relates to an engine arrangement comprising a heat recovery circuit for recovering energy, especially but not exclusively in a vehicle.
For many years, attempts have been made to improve vehicle efficiency, and more particularly the engine efficiency, which has a direct impact on fuel consumption.
One conventional system is to provide the engine arrangement with a heat recovery circuit for recovering part of the energy which is otherwise wasted in the form of heat in the exhaust gases, in the engine cooling circuit, in the lubricating circuit, etc. Such heat recovery circuits include Rankine circuits in which a fluid flows in a closed loop and undergoes successive processes according, to the Rankine thermodynamic cycle:                the working fluid, which is a liquid at this stage, is pumped from low to high pressure;        the high pressure liquid is evaporated into a has by a hot fluid flowing in another circuit of the engine arrangement;        the gas is expanded in an expander;        finally, the gas is condensed.        
As a result, at least part of the thermal energy of the hot fluid used to evaporate the heat recovery fluid is recovered in the expander, for example under the form of mechanical, hydraulic, pneumatic or electrical energy. This thermal energy would otherwise be lost.
However, the provision of a heat recovery circuit involves the implementation of additional lines and components, which requires space and brings weight and cost.
It therefore appears that, from several standpoints, there is room for improvement in engine arrangements.
It is desirable to provide an improved engine arrangement comprising a heat recovery circuit which can overcome the drawbacks encountered in conventional such engine arrangements.
According to an aspect of the invention such an engine arrangement comprises:
an internal combustion engine where a combustion chamber is supplied with at least one combustion fluid by means of at least one combustion fluid circuit comprising at least one combustion fluid pump;
a heat recovery circuit carrying a fluid in a loop, successively through at least a pump, an evaporator, an expander capable of generating power from the fluid expansion, and a condenser,
characterized in that the combustion fluid is used as the fluid in the heat recovery circuit and in that the combustion fluid pump is a common pump located in the heat recovery circuit to pressurize the fluid in the heat recovery circuit.
Thus, in an engine arrangement according to the invention, the heat recovery circuit does, in most cases, not comprise a dedicated pump, the fluid flowing in the heat recovery circuit being pumped from low to high pressure by a pump which is already provided for other purposes, i.e. the combustion fluid pump. Of course, there remains the possibility to provide a further pump in the heat recovery circuit, for example for further elevating the pressure level of the fluid in that circuit. Therefore, thanks to the invention, there can be provided an engine arrangement including a heat recovery circuit for recovering, energy which requires one pump less than in such engine arrangements of the prior art. This results in an engine arrangement which is more compact and less expensive.
It also contributes to a better overall engine efficiency as it spares driving a pump which would otherwise require a fraction of the engine's work.
in concrete terms, the heat recovery circuit is coupled to the combustion fluid circuit, and the same fluid flows, for example from a combustion fluid tank, to the engine and to the heat recovery circuit. Thus, said fluid must be both capable of playing its role in the combustion process in the engine and capable of undergoing the successive processes of a heat recovery cycle. As a result, a flow of combustion fluid flows through the common pump and is later divided into at least two flows, one directed to the combustion chamber and the other directed to the heat recovery circuit.
According to an embodiment, the engine arrangement comprises a low pressure combustion fluid pump and a high pressure combustion fluid pump, the common pump for the combustion fluid circuit and for the heat recovery circuit being the low pressure combustion pump. This applies in particular when the combustion fluid is fuel and where the internal combustion engine is a direct injection engine, either of the compression ignition type such as diesel engines, or of the spark-ignition type, were the fuel pressure after the low pressure pump can be around 3-5 bar. Of course, the engine arrangement may comprise a combustion fluid circuit having a single combustion fluid pump, which is then the common pump.
In any case, the engine arrangement may have several combustion fluid circuits, for example for separately injecting in the combustion chamber two or more fuels, or for injecting fuel and water, or for injection fuel and another type of additive such as an anti-knocking agent. In such case, each combustion fluid circuit may have its own pump and any one of the pumps can be the common pump shared with the heat recovery circuit.
According to a further feature, the heat recovery circuit may further comprise pressure reducing means between the common pump and the evaporator. This may apply in particular to spark ignition engines of the indirect injection type, which are supplied with fuel, such as gasoline, ethanol, methanol, liquid petroleum gas, natural gas or blends thereof. In such engines, fuel is injected in an intake manifold at around 30 bars. Therefore, the fuel pump is capable of raising the fuel pressure to around 30 bar. Then, the heat recovery circuit may require lower pressures for operating optimally, hence the usefulness of providing pressure reducing means being designed to lower the fuel pressure, for example to around 5-10 bar, in the heat recovery circuit.
The combustion fluid which is used as the fluid in the heat recovery circuit may comprise one of or a mixture of                an alcohol such as methanol or ethanol;        a lower alkane amidst methane, ethane, propane or butane;        water,        dimethyl ether (DME)        ammonia-water solution.        
Such fluids are known to be used already either as a fuel, a fuel component or as another combustion fluid component in internal combustion engines, and as a fluid in a heat recovery circuit.
The fluid flowing in the heat recovery circuit evaporated in the evaporator by a hot fluid which can be chosen among:
a coolant of the engine flowing in a coolant circuit downstream from the engine—which therefore has a high temperature;
hot exhaust gases flowing in an exhaust line of the engine arrangement;
engine oil;
compressed intake air of the engine—i.e. hot gases downstream from the compressor;
EGR (exhaust gas recirculation) gases.
For example, the expander in the heat recovery circuit can be chosen among a turbine, a scroll, a screw and a piston.
In an implementation of the invention, the heat recovery circuit may further comprise a heater, also called regenerator, located downstream from the pump and upstream from the evaporator, said heater being designed to preheat the fluid flowing in the heat recovery circuit before it enters the evaporator by means of the fluid flowing in the heat recovery circuit downstream from the expander and upstream from the condenser. Indeed, the fluid which has been expanded has lost thermal energy but nevertheless its temperature remains high enough to preheat the fluid before it enters the evaporator.
The engine arrangement advantageously comprises means capable of recovering the energy produced by the heat recovery fluid expansion in the expander into mechanical energy on the engine crankshaft, into electricity and/or into hydraulic or pneumatic pressure. The mechanical energy can be recovered on the engine crankshaft directly or via intermediate parts such as gears. As regards electricity, it can be produced by means of an alternator coupled to a turbine as the expander. Electricity can be used in a hybrid vehicle (i.e. a vehicle powered by an internal combustion engine and an electric, motor) or in a conventional vehicle to charge a battery, to power auxiliaries, etc.
According to another aspect, the invention relates to a vehicle which comprises an engine arrangement as previously described.
However, the invention may also be used in other applications, for example in fixed industrial systems such as engine arrangements driving fixed electric generators.
These and other features and advantages will become apparent upon reading the following description in view of the drawing attached hereto representing, as non-limiting examples, embodiments of an engine arrangement according to the invention.